Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F3/00—Pistons 
  • F02F3/0015—Multi-part pistons
  • F02F3/0069—Multi-part pistons the crown and skirt being interconnected by the gudgeon pin
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B3/00—Engines characterised by air compression and subsequent fuel addition
  • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F3/00—Pistons 
  • F02F3/0015—Multi-part pistons
  • F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
  • F02F2003/0061—Multi-part pistons the parts being connected by casting, brazing, welding or clamping by welding
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F2200/00—Manufacturing
  • F02F2200/04—Forging of engine parts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2201/00—Metals
  • F05C2201/02—Light metals
  • F05C2201/021—Aluminium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2201/00—Metals
  • F05C2201/04—Heavy metals
  • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2201/00—Metals
  • F05C2201/04—Heavy metals
  • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
  • F05C2201/0448—Steel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2251/00—Material properties
  • F05C2251/04—Thermal properties
  • F05C2251/042—Expansivity

Definitions

• This invention relates generally to a compact engine piston assembly for a high output internal combustion engine, and more particularly to a steel piston member capable of resisting relatively high combustion chamber pressures and temperatures and having machined surfaces of revolution.
• U.S. Pat. No. 4,662,047 issued to Rutger Berchem on May 5, 1987 discloses a one-piece piston produced by die pressing of a previously forged blank to bend an annular cylindrical collar thereon.
• a forged piston can offer the capability of resisting high combustion chamber pressures and temperatures; however, the forging of parts with relatively thin wall sections having extremely close dimensional tolerances and the forming of narrow and deep cavities having precise relative locations is very difficult, if not impossible. Therefore it is fre-quently the manufacturing tolerances that limit or prevent the forging of the thin wall sections and narrow deep cavities that are so urgent required for better heat dissipation.
• Complex shapes and varying wall thicknesses can also result in uneven heat distribution and differential thermal distortion of the piston, so another objective is to simplify the construction as much as possible including maximizing the symmetry thereof about the central axis.
• a high output engine piston assembly having a piston member therefor which is capable of continuous and efficient operation at combustion chamber pressures above about 13,790 kPa (2,000 psi), and preferably in the region of about 15,170 kPa (2,200 psi).
• the piston member should preferably be forged from an alloy steel material having a configuration substantially devoid of complex shapes to allow the forging thereof.
• the region of the upper portion of the piston member and specifically the cooling recess region should preferably have relatively thin, substantially constant wall thicknesses for substantially even heat distribution and for maximum cooling of the surfaces.
• the surfaces of the cooling recess should be machined surfaces of revolution for precise dimension control between adjacent surfaces and especially between the cooling channel and the ring grooves.
• the piston member should preferably include symmetrical surfaces of revolution about the central axis with the surfaces being free of imperfections that could cause the propagation of cracks and so that differential thermal distortion can be avoided.
• the present invention is directed to overcoming one or more of the problems as set forth above.
• a forged steel engine piston member in one aspect of the present invention, includes an upper main portion of generally cylindrical shape and a relatively thin tubular wall depending from the top surface thereof, and having a lower end surface, and an inwardly facing wall surface extending upwardly from the end surface.
• the upper portion also has an annular outwardly facing wall surface spaced radially inwardly from the inwardly facing wall surface and a transition portion connected thereto and to the inwardly facing wall surface to collectively define an annular cooling recess.
• the inwardly facing wall surface, the outwardly facing wall surface and the downwardly facing transition portion are all fully machined surfaces of revolution.
• the piston member further has a lower portion including a pair of depending pin bosses individually defining a bore and with the bores being aligned.
• an engine piston assembly for an engine having a block, a cylinder liner received in the block and defining a bore, and a cylinder head connected to the block.
• the assembly includes a forged steel piston member having an upper portion of a substantially cylindrical shape, a peripheral top surface, and a relatively thin tubular wall depending from the outer edge of the top surface and having lower end surface and a inwardly facing wall surface extending upwardly from the end wall surface.
• the upper main portion also has an annular outwardly facing wall surface spaced radially inward from the inwardly facing wall surface and a transition portion connected thereto and to the inwardly facing wall surface to collectively define an annular cooling recess.
• the inwardly facing wall surface, the outwardly facing wall surface and the downwardly facing transition wall surface are all fully machined surfaces of revolution.
• the piston member further has a lower portion including a pair of depending pin bosses individually defining a bore and with the bores being aligned.
• a lower portion of the forged steel piston member includes a pair of pin bosses blendingly associated with the recess and individually having a bore therein.
• the piston assembly of the present invention has a steel piston member with a non-complex shape so that it can conveniently be forged and machined, is yet has a cross sectional configuration that is capable of resisting combustion chamber pressures in a range in excess of 13,790 kPa (2,000 psi) and is lightweight.
• Fig. 1 is a diagrammatic, fragmentary, transverse vertical sectional view of an engine piston assembly constructed in accordance with the present invention
• Fig. 2 is longitudinal vertical sectional view of a portion of the piston assembly illustrated in Fig. 1 as taken along the line II-II thereof;
• Fig. 3 is an enlarged fragmentary portion of the top peripheral region of the piston member shown in Figs. 1 and 2 to better show details of construction thereof;
• Fig. 4 is a top view of the piston member shown in Fig. 2 as taken along line IV-IV thereof;
• Fig. 5 is a section view solely of the piston member shown in Fig..2 as taken along line V-V thereof,
• Fig. 6 is a top view solely of the piston skirt shown in Fig. 2 as taken along line VI-VI thereof.
• Fig. 7 is an enlarged fragmentary cross sectional view of the top peripheral region of the piston member shown in Figs. 1 and 2 which shows the flow lines of a- simple forged piston member with only a portion of the cooling recess forged;
• Fig. 8 is an enlarged fragmentary cross sectional view of the top peripheral region of the piston member shown in Figs. 1 and 2 which shows the flow lines of a forged piston member with a deeply forged cooling recess.
• a diesel engine 10 of the multi-cylinder type includes a bottom block 12, a top block or spacer portion 14, and a cylinder head 16 rigidly secured together in the usual way by a plurality of fasteners or bolts 18.
• a midsupported cylinder liner 48 has a cylindrical upper portion 52 which is stabilizingly supported by the top block 14 and defines a piston bore 54 having a central axis 66.
• cross reference is made to U.S. Patent No. 4,638,769 issued to B. Ballheimer on January 27, 1987 which further discusses the features and advantages of the multipiece cylinder block with midsupported liner disclosed herein.
• the engine could however be of any conventional design.
• the diesel engine 10 further includes first and second cooling oil directing nozzles 74 and 75 as is shown in the lower right portion of Fig.l.
• the first nozzle 74 is rigidly secured to the bottom block 12 and is operationally associated with a conventional source of pressurized oil, not shown, to supply a narrow jet of engine lubricating oil substantially vertically in a preselected region of an articulated piston assembly 76.
• the second nozzle 75 is also secured to the bottom block ? but is angularly inclined away from the vertical to impinge a jet of cooling oil on another region of the piston assembly 76.
• the articulated piston assembly 76 of the diesel engine 10 includes a forged upper steel piston member 78 and a lower forged aluminum piston skirt 80 which are articulately mounted on a common steel wrist pin or gudgeon pin 82 having a longitudinally orientated central axis 84.
• a conventional connecting rod 90 having an upper eye end 92 and a steel-backed bronze sleeve bearing 94 therein is operationally connected to, and driven by the wrist pin 82.
• the steel piston member 78 has an upper portion 96 of substantially cylindrical shape and a preselected maxi.mum diameter "D" as i.s i.llustrated.
• the upper portion 96 has a fully machined peripheral top surface 98 that is flat, or is located on a plane perpendicular to the central axis 66, and a recessed symmetrical crown surface 100 that in the instant example is a fully machined surface of revolution about the central axis 66.
• the crown surface 100 has a centrally located apex portion 102 elevationally disposed below the top surface 98, a peripheral or outer axial surface 104 and an annular trough 106 that smoothly blends with the apex 102 and the axial surface 104.
• the piston member 78 further includes a relatively thin tubular wall 108 that depends from the outer edge of the top surface 98.
• the overall height identified by the letters "LH" of the tubular wall 108 in this instant example was 31mm.
• the tubular wall defines in serially depending order fully around the periphery thereof a first or top land 110, a top ring groove 112 having a keystone or wedge-like shape in cross section, a second or upper intermediate land 114, an intermediate ring groove 116 of rectangular cross section, a third or lower intermediate land 118, a bottom ring groove 120 of rectangular cross section, and a forth or bottom land 122 that is terminated by a lower radial fully machined end wall surface 124.
• the minimum elevational distance between the top surface 98 and the top ring groove 112, indicated by the letters "TRH" was 5mm.
• An annular, generally axial, inwardly facing tapered wall surface 126 is also delineated by the wall 108 and extends upwardly from the end wall surface 124.
• the body portion 96 of the piston member 78 is additionally defined by an annular radially outwardly facing wall surface 128 spaced radially inward from the inwardly facing wall surface 126 and a downwardly facing transition wall portion 130 that is blendingly associated with the wall surfaces 126 and 128 to collectively define an annular cooling recess 132 of a precisely defined cross-sectional shape. It may be noted that the top of the cooling recess 132 is in juxtaposed elevational relationship with the top of the ring groove 112. It is also elevationally disposed directly underneath the peripheral top surface 98 of the piston member 78 and within an elevational distance therefrom identified by the letter E. In one embodiment the distance "E" was about 5.5mm.
• the wall surface 128 of the instant example is defined by an upper fully conical portion 134 having an inclination angle "A" with respect to the central axis 66 of approximately 12.33 degrees as is shown in Fig. 3, and a fully cylindrical portion 136 below it.
• the wall surface 126 is fully conical and has an inclination angle "B" of approximately 1.17 degrees.
• the inwardly facing wall surface 126, the outwardly facing wall surface 128 and the downwardly facing transition wall portion 130 are all fully machined surfaces of revolution. It may be noted that the radial thickness between the inwardly facing wall surface 126 and the innermost portion of the top groove 112 is slightly larger than the radial thickness of the same wall surface and the innermost portion of the seal ring groove 116.
• the latter radial thickness is the most critical dimension, and in the instant example the minimum acceptable value thereof was 1.74mm. Preferably, such value is 3 or 4mm.
• the seal grooves 112, 116, and 120 are all fully machined surfaces of revolution so that the critical cross-sections radially inwardly thereof are also precisely controlled.
• annular cooling recess 132 could be of any configuration to be forged such as the shallow recess shown in Fig. 7 or as an alternative the deep recess as shown in Fig. 8.
• the grain flows obtained by the different depth recesses are shown by use of phantom lines.
• inwardly facing wall surface 126 it may be only necessary that inwardly facing wall surface 126 be a machined surface of revolution so that the critical cross section between the surface and the seal ring groove 116 be precisely controlled.
• the piston assembly 76 also includes a top split compression ring 138 of a keystone shape which is received in the top ring groove 112, an intermediate split compression ring 140 of a stepped rectangular cross section which is received in the intermediate ring groove 116, and an oil ring assembly 142 which is received in the bottom ring groove 120.
• the steel piston member 78 also has a lower portion 158 including a 5 pair of depending pin bosses 160 blendingly associated with the outwardly facing wall surface 128 of the cooling recess 132 and blendingly associated also with a downwardly facing concave pocket 162 defined by the upper portion and centered on the axis 66.
• the 10 . concave pocket is spaced substantially uniformly away from the apex portion 102 of the crown surface 100 so as to define a relatively thin crown 164 of generally uniform thickness "C" as is shown in Figs. 1 and 2.
• the embodiment illustrated the
• each of the pin bosses 160 has a bore 168 therethrough which are adapted to individually receive a steel-backed bronze bearing sleeve 170 therein. These bearing sleeves 170 are axially aligned to receive the wirist pin 82 5 pivotally therein.
• the piston skirt 80 has a top peripheral surface 172 in close non-contacting relationship with the lower end wall surface 124 of upper piston member 78 with a fully 0 annular, upwardly facing coolant trough 174 defined therein. It further has a slightly elliptical external surface 176 therearound which depends from the top surface 172.
• a pair of aligned wrist pin receiving bores 178 are formed through the piston 5 skirt 80. The piston skirt 80 is thus articulately mounted on the wrist pin 82 which is insertably positioned in both bores 178.
• a pair of axially oriented bosses 184 are defined within the skirt 80 so that a corresponding pair of. lubrication passages 186 can be provided fully axially therethrough.
• the lubrication passages 186 provide for communication with the oil trough 174 and the cooling recess 132.
• the lubrication passages 186 are positioned diagonally opposite each other so that the skirt 80 can be mounted on the wrist pin 82 in either of the two possible positions, and so at least one of them will be axially aligned with the first oil jet nozzle 74.
• the skirt 80 is also provided with diagonally opposite, semi-cylindrical recesses 188 which open downwardly at the bottom of the skirt to provide clearance from the nozzles 74 and 76 when the skirt is reciprocated to it's lowest elevational position.
• the unique forged steel piston member 78 in this application is used with an articulate piston assembly 76.
• the articulated piston assembly 76 is used in a high combustion chamber pressure engine 10 having a combustion chamber pressure of about 15,170 kPa (2200 psi) .
• the piston member 78 allows the specific output to be increased.
• the articulated piston assembly 76 is used with an engine 10 having a mid-supported cylinder liner 48 and a two piece cylinder block 12,14 construction.
• the first nozzle 74 directs lubricating oil into the skirt passage 186 aligned therewith.
• the oil jet continues upwardly whereupon it makes contact with the inwardly facing wall surface 126, the outwardly facing wall surface 128 and the downwardly facing wall portion 130 collectively defining the annual cooling recess 132 of the upper portion 96 of the piston member 78.
• a significant portion of the oil is caught by the skirt trough 174 as the piston assembly is reciprocated where it is advantageously splashed in a turbulent "cocktail shaker" action cooling the peripheral surfaces 126, 128, and 130 of the cooling recess 132 and thus the web 166 and the relatively thin tubular wall 108 defining the ring grooves 112, 116, and 120.
• the second nozzle directs oil in a narrow column against the connecting rod 90 and against the concave pocket 162 or underside of the crown 164.
• the top of the cooling recess 132 is in juxtaposed elevational relationship with the top of the ring groove 112. It is also elevationally disposed directly underneath the peripheral top surface 98 of the piston member 78, and within an elevational distance therefrom identified by the letter E.
• the diameter D was 124mm, and the distance E was about 5.5mm.
• the inner wall surface 126 is a machined surface of revolution about the central axis 66 which permits precise dimensional control and concentricity between the bottom of the ring groove 112, 116, and 120 and the wall surface.
• the inwardly facing wall surface 126 be a machined surface of revolution for dimensional control and concentricity with relation to the bottoms of the ring grooves 112, 116, and 120, and specifically the closest ring groove 116.
• the articulated piston assembly 76 is preferably manufactured in a particular way devoid of complex shapes and by using certain materials.
• the upper steel piston member 78 is preferably forged from a chrome-moly alloy steel material such as a basically 4140 modified steel material.
• the lower aluminum piston skirt 80 is likewise preferably forged an alloy aluminum material such as a basically SAE 321-T6 modified aluminum material.
• the aforementioned alloy steel is particularly adaptable to Class II forging procedures, and can provide an austenitic grain size 5 or finer which is highly desirable to resist the high compression pressures above about 13,790 kPa (2,000 psi) , and preferably above about 15,170 kPa (2,200 psi) .
• Etched cross sectional samples of the forged steel piston member have indicated that the grain flow lines therein are generally or broadly oriented in an inverted U-shaped configuration that roughly approximates the shape of the piston member portion shown in Figs. 3, 6 and 7 and/or roughly aligns the grain flow lines with the web 166 and the tubular wall 108, and this contributes substantially to the cross sectional strength thereof.
• the aforementioned forged aluminum alloy has a high hardness, excellent wear resistance, and a relatively low coefficient of thermal expansion.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)
• Forging (AREA)

Applications Claiming Priority (5)

Publications (2)

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ID=26948755

Family Applications (1)

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• 1988
  • 1988-12-23 US US07/291,429 patent/US4867119A/en not_active Ceased
• 1989
  • 1989-02-23 WO PCT/US1989/000714 patent/WO1990004712A1/en active IP Right Grant
  • 1989-02-23 JP JP1502888A patent/JP2703081B2/ja not_active Expired - Lifetime
  • 1989-02-23 EP EP89903368A patent/EP0398993B1/de not_active Expired - Lifetime
  • 1989-02-23 BR BR898907412A patent/BR8907412A/pt not_active IP Right Cessation
  • 1989-02-23 AU AU32158/89A patent/AU624367B2/en not_active Expired
  • 1989-02-23 DE DE68919074T patent/DE68919074T2/de not_active Expired - Lifetime
  • 1989-08-01 CA CA000607246A patent/CA1322500C/en not_active Expired - Lifetime
  • 1989-10-10 CN CN89107907.6A patent/CN1019892C/zh not_active Expired - Lifetime

Non-Patent Citations (1)

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